1. Field of the Invention
The present invention relates to door locks with integrated electronics. More particularly, the present invention relates to door locks with an integrated sensor to detect whether the door in which the lock is installed is open or closed.
2. Description of Related Art
In recent years, door locks have increasingly been designed with integrated electronics, actuators and sensors. Door locks of this type are typically used in public buildings, businesses and high-end residential applications where it is desired to monitor door usage, detect unauthorized entry and the like. The lock electronics may record or use the monitored data at the lock, or it may send the data for use at another location through a wired or wireless connection.
Generally electronic locks of this type monitor the position of one or more internal lock components. For example, a switch or sensor inside the lock may detect when a latchbolt is extended or retracted. Retraction of the latchbolt is generally associated with usage of the door, but it does not specifically indicate whether the door is open or closed. The door may be held open by placing something between the door and doorframe to prevent the door from closing.
Similarly, a sensor in the lock mechanism may monitor the position of a locking component in the lock to detect if the lock mechanism is in a locked or unlocked state. Typically, if the door is locked, it would not allow access. However, it may be possible for the lock to be in a locked state with the door blocked open.
For these reasons, and others, it is often desirable to directly monitor the door position, i.e., to monitor whether the door is actually open or closed. It is known to perform such monitoring by monitoring the door position with an external sensor of the type commonly used in security and alarm systems. However, using a sensor that is external to the lock makes it difficult for the information about the monitored door position to be directly used by the door lock electronics and/or the central control system for the door locks. Further, an external door position sensor is more difficult to install. It requires additional drilling, mounting and wiring. It is more easily damaged or tampered with.
It is preferable to integrate a door position sensor into the lock mechanism so that installation is simpler, the sensor is more secure and the data from the door position sensor can be used by the security system that controls the locks.
One problem with integrating a door position sensor into a lock is the limited space available for the sensor. Typically, it must be installed at the faceplate along the vertical edge of the door that faces the door jamb (the vertical portion of the doorframe) where the strike is installed. This part of the lock already includes the latchbolt, mounting screws, and may include a deadbolt, guard bolt, and other controls and mounting or installation hardware.
Accordingly, most prior art locks that include a door position sensor position the sensor where the deadbolt is normally installed, and omit the deadbolt. However, this is a less secure lock design than one that includes the deadbolt and, as such, it is not suitable for high security applications. There is a need for a door position sensor design that does not require omitting the deadbolt.
A magnetically actuated door position sensor is preferred over a mechanical switch. Magnetically actuated sensors tend to be more rugged and less visible, which is preferable for high security applications. However, it is often difficult to integrate a magnetic sensor into a lock because lock mechanisms typically have many components made of steel, iron or other magnetic materials, all of which potentially interfere with the operation of a magnetic sensor.
Further, with a magnetically actuated electronic sensor it is desirable to position the sensor in the lock mechanism and a magnet in the door strike. However, the door strike is typically made of steel, which can interfere with the magnetic field. The strike includes one or more relatively large openings for the latchbolt and deadbolt, as well as screw openings for fastening the strike to the door jamb. These openings severely limit the space available for the magnet.
Even more specifically, the dimensions of the strike and mortise openings (or strike and bored openings for bored locks) are generally set by industry standards. Doors and door frames are constructed with openings having these standard dimensions. These standardized dimensions are typically referred to as the “door prep” and openings that meet these standards are commonly provided with the door and frame. They are not subject to change. Locks and strikes must be constructed to match if they are to also meet industry standard specifications. It would be undesirable, in any case, to expand the size of the strike, as this may indicate the presence of a door position sensor to unauthorized persons.
Much of the limited space in industry standard door prep openings is already used for the latchbolt, the deadbolt and any guard bolt, plus the screw openings used to mount the strike and lock mechanism. As indicated above, these space limitations have heretofore typically required that the deadbolt be omitted when installing a door position sensor. The space made available by omitting the deadbolt has then been used to provide space for installing a door position sensor. There is a need for a door position sensor design that can be used with a deadbolt lock that meets industry standard specifications and fits within the limited space available. There is also a need for a door position sensor design that can be retrofitted to work in the extremely limited space available of existing door lock and door strike designs.
A related problem is that a mortise lock typically has a case and a decorative “faceplate.” The front edge of the mortise lock case (the “front plate”) and the decorative faceplate are both typically made of magnetic materials, which cause problems with magnetic sensor designs.
The combination of limited space with the necessity to “hide” the magnets, coupled with the problems of magnetic materials have all made it very difficult to provide a reliable door position sensor for locks, particularly for mortise locks having a deadbolt. The problem is particularly acute when the door is hung poorly with a gap between the door and the strike plate that is greater than usual. This weakens the magnetic field extending from a magnet in the strike plate towards the lock to the point that a magnetic sensor located in the lock may no longer be able to detect the weakened field when the door is closed. This results in an erroneous indication that the door is open.
Although it might seem to be desirable to extend the sensor into the gap area, this cannot be done, as it would make the sensor visible, subject to attack and damage and potentially would interfere with operation of the door.
With respect to bored locks, the small size of the strike (as compared to the strike for a mortise lock with a deadbolt) creates similar problems, particularly for bored in locks having a two piece front plate similar to the faceplate/front plate design for a mortise lock.
Accordingly, a need exists in the art for improved door lock designs having an integrated door position sensor in which the sensor is very small, to fit beside a deadbolt or in limited available space. The improved design or method must allow the sensor in the lock to reliably respond to a magnetic field from a magnet located in an associated strike, even when the gap between the lock and strike, after installation, exceeds industry standards.